Method and apparatus for determining the force of gravity



March 3, 1936. P. P. sTouTENBURGH METHOD AND APPARATUS FOR DETERMINING THE FORCE OF GRAVITY 3 Sheets-Sheet 1 Filed Dec. 16, 1927 /lvve/vraR .2 l l i PAUL F? Sraurfneunef-l @ww ATTORNEY Sw wmf. 5

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NIN 47( l March 3, 1936.

P. P. sjrouTENBuRGH 2,032,381 METHOD AND APPARATUS FOR DETERMINIG THE FORCE OF GRAVITY.

Filled nec. 16, 14927 s sheets-sheet z /NvE/vrae PA ul. l? SroureueueGH fmwemybm.

4ATTORI/v5 Y March 3, 1936. P. RSTQUTENBURGH -METHOD ANDy APPARATUS FOR DETERMINING THE FORCE OF GRAVITY Filed Dec. 1.6, 1927 3 Sheets-Sheet 3 vHwENToR PAUL FZ Sicilie/Yanes Yowa MTTQRNEY Pani lllytoutenburgh, Washington, lli. i). Application December liti, ilZ, Serial No. Zlilti 3 Claims.

(Granted under the act of March 3,

amended April 30,

.The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes only Without the payment to me o1 My invention relates apparatus for determining the earth at points belo any royalty thereon. broadly to methods and W the surface and more particularly to methods and apparatus for determining the presence of oil and ore deposits therein.

vOne object of my invention is to utilize the variable be surveyed to vary the force of gravity existing in the area to constants of an electrical circuit in such a manner that the frequency of a high. frequency current generated therein may be measured and determined as a function of the force of gravity.

Another object of my invention is the provision of means for and method of measuring the relative changes in the force ing mathemetical or gravity as an increasfunction of the changes in the force of gravity'as the force of gravity increases.

Further objects of my more fully hereinafter as invention Will appear the description of the method and apparatus is developed.

It is Well known, as determined by the activities of the geological surveys carried on by thev British and United States force ofv gravity varies in Governments, that the proportion to the density of the major portion of the earths crust directly below the point Where the measurement is to be taken.

In the apparatus that utilized this principle I have developed I have to vary the frequency of a high frequency current and then measured the frequency of that current as a function of -the force of gravity. Although I have shown a specific instrument for such a measurement, it is to be understood that many types of apparatus may be utilized Within the scope of the appended method claims Without departing from the spirit of my invention. Such which the generated in a circuit electric crystal is varied an apparatus is one in frequency of an electrical current controlled by a piezoby the varying pressure exerted upon the crystal by the varying force of gravity.

My invention consists substantially in the construction, combination and arrangement of parts associated therewith or as Will be more fully here inafter set forth as shown by the accompanying drawings and iinally pointed out in the appended claims.

'Reference is to'be had to the accompanying drawings forming a par t of this specification in the relative density of (Uil. IVW- 351) which like reference characters indicate corresponding parts throughout the several views and in Whichz- Figure 1 is a side elevational view of the instrument with the side of the cabinet broken away to Figure 2 is a front show the internal arrangement of the parts', elevational view showing the arrangement of instruments upon they cabinet panel as co-ordinate shown in Figure 1,

d with the instruments Figure 2a is a modiiication of the gravity sensitive elements shown in Figure Figure 3 is a top plan view of the cabinet with the levelling gauges -in Figure 4 is a` detail position,

structural vievv of the Agravity sensitive element,

Figure 5 is a circuit diagram ofthe electrical elements of the device, and Figure 6 is a circuit diagram embodying piezoelectric crystal means.

Referring particularly designates the legs of a tripod, j head 2, which carries a plate are threaded a plurality of to Figure i, numeral l oined to a tripod 3. Into this plate levelling screws 4 which in turn are reversely threaded into a plate 5 that is secured to the element l. head are similar to tripod and function in the cabinet as indicat levels positioned upon Figures l, 2, and 3.

The cabinet 'i is of cabinet il by means of an The levelling screws and the tripod those used upon a transit a similar manner to level ed upon the rightangled the cabinet as shown in portable size and is constructed of heat insulating material similar to that used in refrigerators. I have formed a containerk y'Within the cabinet for the storage of ice or for apparatus capable of maintaining a fairly constant temperature within the cabinet.

The vvallsl of the container are such that the cabinet will flow-of currents of air Within the transfer heat therethrough.

Referring to Figure compartment 9 within or" batteries which are 2, I have also provided a the cabinet for the storage to be connected to the electrical apparatus to be hereinafter described. En-

trance is gained to the `to the compartments hinged to the base of closed position by In the upper portion interior of the cabinet and t and t through doors it the cabinet and held in means of locks l.

of the cabinet I have provided the gravity sensitive element in a position shown in Figures l and 2. rI'hs device, shown in detail in Figure 4, cons tral portion of which i ends of which rest in ists of a shaft i i, the cens U shaped'and the outer bearings l2 and i3 in the walls of the cabinet. The end I4 of the shaft extends through the wall of the cabinet and terminates in a dial I5 which may be calibrated in a manner hereinafter described. 'I'he other end I6 of the shaft 'extends through the wall of the cabinet and terminates in an adjustable friction member. This friction member consists of a-friction plate I1 that is resiliently pressed against the end of the bearing I2 by means of a spring I3 and a nut i3 which is threaded upon the shaft.

Between the ends of the U shaped shaft and in alignment with the rotational axis thereof, I have provided a plurality of torsional members 23, the outer ends of which are aillxed to the shaft. One end of one of the torsion members is lclamped to the end I4 of the shaft Il by means of a screw 2 I which is threaded into the shaft in such a manner that it binds the enlarged end of the torsion member 20 against the end of the chamber 23' formed in the shaft. i

One end of the other torsion member 23 is rigid- 1y welded to a threaded member 22 which extends into a pocket 23 in the end I6 of the shaft Il. 'I'he member 22 is adjustable longitudinally of the axis of rotation of the shaft by means of a knurled thumb nut 24 that extends into a slot in the shaft and is threaded upon the member 22. The member 22 is fixed relative to any rotational movement with respect to the shaft Il by means of a pin 25 which extends through the metal of the shaft and through a slot 26 in the member 22.

The inner ends of the torsional members 2l are rigidly affixed to a rotational member 21 which consists of a body portion 23, bearing surfaces 23 and minute pinions 30 upon each end of the body portion. 'I'he union between the torsional elements 20 and the ends of the pinions 33 may be made by welding or, in case other than metallic torsional elements are used, by mechanical means.

Mounted upon the U shaped portion of the shaft are two adjustable bearing braces 3| which carry jewelled bearings 32. These bearings have conical portions 33 which correspond to the conical bearing portion of the rotational member 21 and have holes extending from the apex of the conical bearing surfaces through the jewel 'of sumcient size that the pinions 33 may-freely extend therethrough.

Upon the rotational member 21 I have provided an arm 34, which may be integral therewith, or clamped thereon by a clamping means 35 as shown. Upon the outer end of the arm, or suspendedtherefrom is a weight of large area and of such size that minute changes inthe force of gravity will displace it from a position which is balanced by the torsional members 2l. Beneath the position of rest of the weight 36 I have provvided a fiat plate 31 which forms a capacity condenser with the weight 36 when considered as electrically related. 'I'his plate has a thin coating of insulating material over its surface to prevent short circuiting of the condenser in the adjustment of the shaft I I about its axis t0 regulate the torsion of the members 23. 1

I vhave arranged the plates as shown for the obvious reason that as the plate 36 approaches the plate 31 the increasedelectrical capacity is more than in the types wherein the relative movement between the plates is that of one over the other. However, it is to be understood that the operation of my invention is the same whether the plates 36, 31 are of the form shown in Fig. 2 or are curved as shown at 36', 31' of Figure 2a, the

yelement i4 being the center of curvature of the In the lower pox-tionA of the cabinet and adjacent the batteryvcompartment and the constant temperature comparment I have placed two vacuum tubes 3l and 33 with a radio frequency transformer 43 therebetween. This 'arrangement is merely optional for there are a variety of radio circuits which would be applicable-to such a device without departing from the spirit of my invention.

The transformer 43 consists of two secondaries and two regenerative coils electrically connected to the tubes 36 and 33 in the manner shown in Figure 5. One of the secondaries is connected to the plates 36 and 31 by wires 4| and 42 as shown in Figure 1 as attached to the metallic elements supporting them. The other of the secondaries is shunted by a variable condenser 43.

The condenser 43 consists of a plurality of stator plates 44 arranged in a parallel frame and rigidly fastened together. The rotor plates 45 are rotatably mounted on a single shaft and movable with respect to each other and each consists of a straight line frequency plate which carries an arm 45' that is actuated bya plunger of insulating material 46 adjustable to a plurality of definite positions as indicatedby the catches". The plates of this condenser are of such a size that when taker. with Ithe other constants of the apparatus, namely, the area of the plates 36 and 31, the value of the torsion members 23 and the value of the secondary across which they are shunted, the number of movable plates in active capacity relationship with the stator plates bears a certain relationship to the change in the value of gravity at that particular point.

Referring to Figure 5, the construction and operation of the device are as follows: 'I'he two vacuum tubes oscillators 33 and 39 are indicated diagrammatically with grids, filaments, and plates. The variable condenser 43 indicates the variable capacity between the plates 36 and 31. It is to be noted that the two secondarles 53 and 5I and the two regenerative coils 52 and 52 are wound upon one form and are mutually coupled together. Each of the filaments of the tubes 33 and 33 are supplied with heating current from batteriesA 53 and 54 through variable rheostats 55 and 56. The plates of the tubes 33 and 33 are supplied with current from a battery 51 R controlling` the frequency generated in the circuits associated with the tubeh 36 as hereinbefore described. The plates 36 and 31 serve in this instance as electrodes for the piezo-electric crystal, 36 being the gravity sensitive element (shown as enlarged in cross section in the drawings)` and 31 being the stationary element as described with reference to Figs. 2 and 2-A.

In order to ascertain the relative frequenciesA of the currents generated by the two oscillator systems I have provided a set of head telephones 53, for which I have supplied the usual telephone Jack 53, in order that the zero beat determination of frequency may be applied. The variable condenser 43 is the same as thatmention'ed in the description of Figure 2 and constitutes the means for bringing the two high frequency currents generated by the two oscillator systems to the same frequency. It is to be understood that any modification of the circuits to utilize the same sources of power or the celestiu-u o?? other means for determining the frequency the currents generated is within the scope of the appended claims.

The constants of the inductances and capacities of the electrical circuit should be such that as the capacity between the plates 3S and changes in a very small degree the resultant change in frequency of the` current in the secondary will be large. The size of the inductance i should be such that there must be a large change in the capacity of the condenser it to change the frequency of the current generated by the vacuum' tube oscillator its to the same value as that generated by the vacuum tube oscillator Although different operators might choose different calibrations the one that have found most useful is that in which the calibration of the dial l5 is such-that the indices of the torsion elements may be maintained at a constant value even though the temperature within the cabinet should change as indicated by the temperature gauge 5t, shown in Figure 2. As above mentioned the value of the condenser plates or condenser it should be such that the number of rotor plates in active capacity relationship with the stator plates indicate a certain relative change in the force of gravity acting upon the movable plate 3b.

In order that the plates 36 and 3i may not be attracted together it is to be noted that the irequency of the current generated in the two Ivac-v uum tube oscillators must be sufficiently removed from the resonant mechanical frequency of the gravity sensitive element that there will be no mechanical swinging of the device. However, with the frequency of the alternating current established at a value above 500 hilocycles the vibratory eiect of the changing and discharging of the condenser plates appears to have no effect whatever upon the plates 3@ and 3l.

liter the device has been calibrated in the iollowing manner the procedure of Operation is as follows:

The instrument is set up, and levelled, the

plates s@ and 3l moved apart by the rotation of the dial l5 which produces a torsion upon the members 2li, with the oscillator tubes both generating current and with a given number o the rotor plates of the condenser in active capacity relationship with the stator plates which setting gives a zero beat between the two high frequency currents as indicated by the head-telephones, the temperature within the cabinet is determined as indicated by the temperature sensitive element 50. The dial i5 is then rotated until zero beat between the two high frequency currents is again obtained. The calibration of the dial i5 is then made to correspond to the zero beat of the currents at any particular temperature.

With the value of gravity known at this particular point this setting of the condenser te corresponds to that value. The device is then moved to different places where 'the value of gravity is known and, for the particular temperature adjustment, the condenser i3 is varied until zero beat is again obtained between the two currents.

In the transportation of the device from place to piace l have found it suilicientv to lower the plates 3@ and 3l together, they being insulated by the thin nlm of insulating material placed over the plate 3l. -i-liowever, any device which will clamp the weight 3i in any position during rthe electrical stress on a dfelec the L'- r gravity sensi jarring is wi inventi f With instrument calibi levelled and the procedure or the tion repeated, the setting of the c' tc obtain Zero beat between two quency currents will give ev of the ,force oi gravity iat particu no lin each o the loregoing instruments it will be seen that T. provided throughout the area ci s lielectric, in instance the dielectric bein which is uniformly varied in accordance vwi variations in the torce of gravity ai other the dielectric being the piezo-elec and the stress thereon being uniformly dis ed over the surface of said crystal. in each oi these instances the variation in the stress is as a direct mathematical unction or the force or gravity. ln'. each or" these instances there is a high frequency current generated, the frequency or which is determined by the stress in said dielectric and each. instance the frequency oi the high frequency current generated, as a result o the change in stress in said dielectric, is meascred.

in each of the three illustrative embodiments of my invention hereinbeiore described. the frequency o the current generatedvaries inversely as an increasing mathematical tunction-that is to say, the change in frequency increases at a rate greater than the rate of change in the force of gravity as the force or gravity becomes greater. ln other words, the sensitivity of the devices becomes greater as the percentage change in the force ci gravity becomes smaller. For example: As the instrument approaches an area where the force of gravity is greater the sensitivity ci the instruments becomes greater enabling the user to detect and measure with greater accuracy the decreasing percentage changes in the force or gravity.

1t will be understood that the above description and accompanying drawings comprehend only the general and preferred embodiment of my invention and that minor detail changes in the construction and arrangement ci' parts may be made within the scope of the appended claims without sacrificing any of the advantages of my invention.

Having thus described my inventionA what claim is:-

l. In a deviceof the class described, the combination of `a tixed member, a torsion element, a gravity sensitive member attached to said torsion member, means for mounting the gravity sensitive member so that it tends to inove toward said xed member on increase in the force of gravity, means for relieving the torsionmember of vertical and lateral loads created by the gravity sensitive member while permitting the transmission of torsional strain thereto, and means for indicating variations in the strain in said torsion element.

2. in an apparatus for determining the force or gravity, a piezo electric crystal, a gravity sensitive element associated with said crystal and arranged to mechanically stress said crystal as a function o the force of gravity, means for sustaining oscillations in said crystal which vary in frequency as a runction'oi the mechanical stress applied to said crystal, and means for measuring Z5 the frequency of the oscillations sustained in said crystal to determine the force of gravity.

3. 'Ihe method of determining the force ot gravity over different areas, which comprisesl varying the mechanical stress applied to a piezo electric crystal as a function of the force of gravi- 

